Conventionally, with respect to a mechanical part which can be used in various fields, there has been known a mechanical part provided with a shaft which is rotated or moved in a reciprocating manner. To name specific examples of such a mechanical part, a motor or a pump provided with a drive shaft, a cylinder provided with a rod and the like can be named.
There is a case where such a mechanical part includes a shaft seal device such as an oil seal or a mechanical seal for preventing a leakage of a liquid from the periphery of a shaft.
For example, in case of a liquid feed pump, a shaft seal device is adopted around a drive shaft for preventing a leakage of a liquid to be fed along the drive shaft.
In case of the cylinder which is driven by a liquid pressure, a shaft seal device is provided for preventing a leakage of a working fluid along a rod.
It is necessary to bring these shaft seal devices in a state where friction resistance is made as small as possible to prevent the friction resistance from obstructing driving of the shaft seal device while maintaining sufficient liquid lightness, and various constitutions have been proposed for this end heretofore.
For example, in a so-called oil-seal-type shaft seal device disclosed in patent document 1, liquid tightness is realized while allowing a shaft to be slidable by bringing a rubber-made lip seal arranged on an outer periphery of a shaft coaxially into contact with a surface of the shaft.
A so-called mechanical-seal-type shaft seal device disclosed in patent document 2 includes: a rotary ring mounted on a sleeve which is rotated together with a shaft; and a fixed ring which is brought into slide contact with the rotary-ring on a slide surface perpendicular to the shaft, and the shaft is made rotatable while maintaining liquid tightness on the slide surface.